diff --git a/contrib/libdiff/lib/diff_main.c b/contrib/libdiff/lib/diff_main.c
--- a/contrib/libdiff/lib/diff_main.c
+++ b/contrib/libdiff/lib/diff_main.c
@@ -54,7 +54,8 @@
 static int
 read_at(FILE *f, off_t at_pos, unsigned char *buf, size_t len)
 {
-	int r;
+	ssize_t r;
+
 	if (fseeko(f, at_pos, SEEK_SET) == -1)
 		return errno;
 	r = fread(buf, sizeof(char), len, f);
@@ -173,7 +174,7 @@
 				    buf_left, n_left);
 			if (r) {
 				*cmp = 0;
-				return r;
+				return (int)r;
 			}
 			p_left = buf_left;
 		} else {
@@ -186,7 +187,7 @@
 				    buf_right, n_right);
 			if (r) {
 				*cmp = 0;
-				return r;
+				return (int)r;
 			}
 			p_right = buf_right;
 		} else {
@@ -196,7 +197,7 @@
 		r = buf_cmp(p_left, n_left, p_right, n_right,
 		    ignore_whitespace);
 		if (r) {
-			*cmp = r;
+			*cmp = (int)r;
 			return 0;
 		}